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() Changes in growth and thyroid function of American kestrels exposed to environmentally-relevant polybrominated diphenyl ethers.

Fernie, Kim1, Mayne, Greg1, Shutt, J2, Letcher, Robert3, Drouillard, Ken3, 1 Canadian Wildlife Service, Burlington, Ontario, Canada2 National Wildlife Research Centre, Canadian Wildlife Service, Ottawa, Ontario, Canada3 Great Lakes Institute of Environmental Research, University of Windsor, Windsor, Ontario, Canada

ABSTRACT- Polybrominated diphenyl ethers (PBDEs) are a class of flame retardants with structural similarity to polychlorinated biphenyls, and are ubiquitous and bioaccumulative environmental contaminants. Over the last decade, there has been an exponential increase in tissue concentrations in certain wildlife and human populations in the world. Changes in the development and thyroid function of American kestrel (Falco sparverius) nestlings were assessed following their in ovo and dietary exposure to environmentally-relevant PBDE congeners and concentrations. Eggs within each clutch, divided between groups by laying sequence, were injected with safflower oil or Penta-BDE congeners BDE-47, -99, -100, and -153 dissolved in safflower oil (18.7 g total () PBDEs/egg), approximating current levels in Great Lakes herring gull eggs. For 29 days, nestlings consumed the same PBDE mixture (15.6 ± 0.3 ng/g body weight/d). Relative congener abundances in the dosing mixture compared to the carcasses suggests biotransformation of BDE-47; BDE-183 was also detected in the carcasses. PBDE-exposed nestlings were larger (weight, bones, feathers) because of greater food consumption, itself a function of PBDE concentrations. BDE-100 was the most influential congener on nestling growth, being positively associated with larger size, faster growth, and greater food consumption. Increasing concentrations of BDE-183 and -153 were correlated with increasing bone length, and BDE-99 with longer feathers. The growth of birds is partially governed by the thyroid hormones, thyroxine (T4) and triiodothyronine (T3). Relative to the controls, the PBDE-exposed nestlings had significantly lower plasma T4 concentrations which were negatively correlated with BDE-47, BDE- 100, and BDE- 99. However, T3 levels and thyroid gland structure were comparable between the two groups of nestlings, and were not correlated with any of the PBDE congeners. The results of this study indicate that the PBDE concentrations currently found in Great Lakes and European birds, are capable of affecting the growth and thyroid function of nestlings.

Key words: birds, thyroid hormones, polybrominated diphenyl ethers, development

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